Girardi, Daniele2024-04-262021-06-23202110.7275/23485220https://hdl.handle.net/20.500.14394/22293This paper surveys the neoclassical theory of aggregate investment and its criticisms. We identify four main strands in neoclassical investment theory: (i) the traditional Wicksellian model; (ii) the Fisherian ‘array-of-opportunities’ approach; (iii) the Jorgensonian model; (iv) the now prevailing adjustment cost models. We summarize each approach, discuss the main conceptual issues, and highlight similarities and differences between them. We also provide a systematic summary and discussion of the main criticisms that have been leveled at each of these models and highlight some unresolved theoretical issues.UMass Amherst Open Access Policyinvestmentinterest ratemonetary policytax policyacceleratorneoclassical economicsadjustment cost modelsEconomicsWorking Paper